Data storage arrays are used to provide large amounts (e.g., 10 terabytes to 10 petabytes) of data storage to enterprises. An example of such a data storage array is a VNX® brand array produced by the EMC Corp. of Hopkinton, Mass. Storage commands are sent by a host computer also connected to the storage network to a storage processor of the data storage array. A typical data storage array typically has two storage processors to allow for load balancing and high availability.
In some systems, each storage processor contains a cache configured as a write-back cache in order to speed performance. In order to increase reliability, many systems enable cache mirroring between the caches of two storage processors, so that cache writes are normally not confirmed until stored in both caches. These systems typically operate in an active/passive configuration, in which one storage processor is regarded as the active storage processor for certain areas of storage, while the other storage processor is regarded as the passive storage processor for those areas, the passive storage processor serving primarily as a backup for the certain areas of storage.